The objective of this project is to characterize the prechronic toxicity of AIDS Therapies. The NIEHS, through its resource dedicated to the National Toxicology Program, is conducting toxicological evaluations of promising AIDS therapeutics in collaboration with NCI, NIAID, FDA, and private pharmaceutical firms. The NIEHS program will provide a focus for comparative toxicity studies as well as studies on combination treatments. In the combination studies, emphasis will be on obtaining baseline data on single drug toxicity before beginning combination studies. The potential for prechronic toxicity studies of DDC and alpha interferon singly, DDC in combination with AZT, and alpha interferon in combination with AZT are being investigated. These prechronic studies are done in a well developed rodent model system, emphasizing investigation of neurobehavioral, bone marrow, and reproductive toxicity, as well as of target organ damage and drug distribution and uptake.